Napoleon made him a Marshal of the Empire in 1804. Lefebvre commanded a division of the Old Guard in the German campaign of 1805. At the Battle of Jena-Auerstedt, on 14 October 1806, Lefebvre commanded the infantry of the Imperial Guard. He besieged and took Danzig in 1807, which won him the title of Duc de Danzig (Duke of Danzig).

He never forgot the hard work that brought him rank and wealth. When a friend expressed envy of his estate, Lefebvre said "Come down in the courtyard, and I'll have ten shots at you with a musket at 30 paces. If I miss, the whole estate is yours." The friend naturally declined this offer, and Lefebvre then added, "I had a thousand bullets shot at me from much closer range before I got all this."